On a graph the numbers on the y axis are: 10, 20 and 30. On the x axis the numbers are: 5, 10, and 15. There is a point in between 20 and 30 and the next point being on 10 on the x axis. With a negative slope. Is this proportional? What is the y intercept? What does the y intercept mean in context of this scenario? What is the slope? What does the slope mean in context of this scenario?

1 answer

To determine whether the relationship in your scenario is proportional, we first need to clarify what proportionality means. A relationship between two variables is considered proportional if it can be described by the equation \( y = kx \), where \( k \) is a constant. This means that the ratio of \( y \) to \( x \) is constant.

From your description:

  • Points on the y-axis are 10, 20, 30.
  • Points on the x-axis are 5, 10, 15.
  • You mention a point between 20 and 30 (let's assume it is 25 for illustration) and another point being on 10 on the x-axis.

If a point is between 20 and 30 on the y-axis and at 10 on the x-axis, that could represent a coordinate (10, 25). However, we need more points to determine if the relationship is linear or proportional and to calculate the necessary parameters.

To analyze:

  1. Determine if the relationship is proportional:

    • With only one point given (10, 25), we cannot definitively say whether the relationship is proportional. We would need at least two points to calculate the slope and check if \( \frac{y}{x} \) is constant.
  2. Calculate the slope:

    • Assuming there is another point given (for example, (5, 20) or similar), we can calculate the slope (m) using the formula: \[ m = \frac{y_2 - y_1}{x_2 - x_1} \] For two given points (5, 20) and (10, 25): \[ m = \frac{25 - 20}{10 - 5} = \frac{5}{5} = 1 \]
  3. Find the y-intercept:

    • The y-intercept (b) can be found from the slope-intercept form of the equation \( y = mx + b \).
    • Using (10, 25) to solve for b: \[ 25 = (1)(10) + b \ b = 25 - 10 = 15 \]
  4. Interpret the meaning of the y-intercept:

    • In the context of this scenario, the y-intercept (15) signifies the value of y when x = 0. It can be interpreted as the baseline value of y before any contribution from x.
  5. Interpret the slope's meaning:

    • The slope (1) indicates that for every unit increase in x, y increases by 1 unit. In a contextual situation, this could mean that there is a direct and constant relationship between x and y.

Conclusion:

Based on your description, more detailed data would clarify the relationship between x and y. If multiple points consistently exhibit a relationship where \( y/x \) is constant, then it would be proportional. The slope and y-intercept interpretations would depend on the specific context of the variables x and y in your scenario.